1. Field of the Invention
In order to establish an environment of terminal mobility, which is one of the advantages of a LAN, in a wide LAN environment using the Internet or intranets, it is necessary to specify the access location of each terminal in such a network; thus, detection of connection and disconnection of each terminal is required. Among these functions, the present invention relates to a technique for realizing detection of terminal disconnection. This application is based on a patent application No. Hei 8-145854 filed in Japan, the contents of which are incorporated herein by reference.
2. Description of the Related Art
In order to establish an environment in which terminals can move in the Internet or intranets to which plural sub-networks are connected (that is, a Virtual LAN or VLAN system), it is necessary to provide a terminal management table for managing terminal (access) location in a router which accommodates terminals, or the like, and to automatically update this table in accordance with movement of the terminals. An apparatus having such a function is called a "client". In addition to providing such a client, specification of the location of each terminal is required for realizing movement of each terminal to any point in the above networks. For such a requirement, detection of terminal disconnection is necessary. In conventional disconnection processes, a user of a terminal to be disconnected gives instructions indicating that the terminal will soon be disconnected, and the client is informed of results of the disconnection. However, in this method, it is necessary to add a special function in each terminal, and thus there has been a problem in that terminals on the market cannot be directly used with their original specification.